Noise reduction techniques for digital pictures are understood in the art. A tradeoff commonly exists in that more aggressive noise reduction can make a picture less noisy, but often results in making the picture blurry or unnatural. In particular, very aggressive noise reduction can reduce low-frequency (wide grain) noise to an acceptable level. However, such noise reduction can also make a picture devoid of nearly all high frequency content, which makes the picture look unnatural. For example, the aggressive noise reduction can make smooth areas, or areas of low-contrast signals appear completely flat.
It is desirable to have methods of digital picture noise reduction that achieves both high levels of noise compression and maintains a natural look to the picture.